No abstract

Phorbolester-triggered differentiation of SH-SY5Y neuroblastoma cells requires serum and a prolonged activation of protein kinase C (PKC). Under serum-free conditions development of a mature phenotype requires phorbolester in combination with a member of either the insulin-like growth factor (IGF) or the platelet-derived growth factor family. Here we report that basic and acidic fibroblast growth factor (FGF) and epidermal growth factor, but not nerve growth factor, synergistically potentiate phorbolester-induced differentiation. Alone these factors induced a mitogenic response which varied in magnitude, with basic FGF and IGF-I being the two most potent mitogens. However, a combination of basic FGF and IGF-I induced differentiation as judged by morphology and the increase in growth associated protein (GAP-43) and neuropeptide tyrosine mRNA levels. In contrast to the phenotype obtained in the presence of phorbolester, bFGF and IGF-I-treated SH-SY5Y cells retained their capacity to proliferate. Finally, in these cells, the phosphorylation of the endogenous PKC substrate, myristoylated alanine-rich C-kinase substrate (MARCKS), was slightly increased during several days, suggesting an involvement of PKC in the bFGF and IGF-I-induced differentiation.

In this group of patients with advanced midgut carcinoid tumours and progressive disease, octreotide pamoate managed to improve symptoms, and stabilise hormone production and tumour growth in 75% of the patients. We believe that high-dose treatment with somatostatin analogues can be an important addition to the therapeutic arsenal for patients with advanced progressive midgut carcinoid tumours.

SUMMARY:Expression of full-length trkB can be found in some highly malignant neuroblastoma tumors with an amplified MYCN gene. This contrasts sympathetic neuroblasts, from which neuroblastomas are thought to arise, which neither express trkB nor are dependent on the p145 trkB ligands, brain-derived neurotrophic factor (BDNF) or neurotrophin-4/5, for their normal development. In this study we show that trkB was expressed in two out of five neuroblastoma tumors with amplified MYCN, while no trkB expression was observed when the MYCN gene was overexpressed in a non-MYCN-amplified neuroblastoma cell line. This shows that MYCN overexpression per se is not sufficient to induce trkB expression. trkB expression and BDNF responsiveness in neuroblastoma cells can be induced by all-trans-retinoic acid (RA). When SH-SY5Y cells were stimulated with a combination of RA and BDNF, norepinephrine and tyrosine hydroxylase levels were unaltered, showing that the cells did not change toward a more catecholaminergic sympathetic phenotype. However, expression of growth-associated protein 43, indicative of a neuronal phenotype, was elevated. Vesicular acetylcholine transporter, choline acetyl transferase, and neuropeptide tyrosine mRNA levels also increased in RA-BDNF-treated cells, which could suggest that these cells develop into a sympathetic cholinergic phenotype. In addition, treatment with RA-induced expression of the platelet-derived growth factor receptor-␣. As previously shown for BDNF, platelet-derived growth factor stimulated growth of the RA-treated cells, findings that could have clinical relevance. If these receptors mediate a mitogenic signal in vivo also, this might limit the effect of RA treatment on neuroblastoma patients. (Lab Invest 2003, 83:813-823).T he childhood malignancy neuroblastoma is derived from cells of the developing sympathetic nervous system. The neuroblastoma cells are arrested at immature stages of sympathetic differentiation, although the stage of tumor cell maturation varies from one tumor to another and often also within a single tumor. This immaturity is frequently manifested in phenotypic characteristics resembling those of sympathetic progenitor cells such as expression of the embryonic and fetal transcription factors dHAND and human achaete-scute homolog-1 (HASH-1) (Gestblom et al, 1997(Gestblom et al, , 1999Hoehner et al, 1996a;Påhlman and Hedborg, 2000). Such progenitor cells give rise to three major closely related, sympathetic cell lineages: the neuronal/ganglionic, the small intensely fluorescent, and the chromaffin cell lineages (Patterson, 1990). The hormones and growth factors determining rat sympathetic progenitor cell lineage selection are grossly understood and involve glucocorticoids, classical growth factors, and neurotrophins (Anderson, 1993(Anderson, , 1997. For example, development into and along the neuronal lineage requires sequential exposure to insulin-like growth factors, basic fibroblast growth factor, and the neurotrophins nerve growth factor (NGF) and neurotrophin(NT)-...